Known methods for filling a gap between an existing conduit and a lining material provided inside the conduit include, for example, a method described in Patent Literature 1. This document describes a method for filling a gap with a filler material, the gap being between an existing conduit and a liner structure fixed inside the conduit. According to this method, an air removing tool is fitted into an air removing hole bored through the liner structure, and the filler material is injected through a filling port while air in the gap is discharged through an opening at a leading end (inserted end) of the air removing tool. The leading end portion of the tool has a shape like a bamboo spear (“bamboo-spear shape”). The filler material enters the air removing tool when the level of the filler material injected in the gap reaches the opening of the tool, and the filler material having entered the tool exits through a rear end (end opposite to the leading end) of the tool. Patent Literature 1 describes that the outflow of the filler material from the tool indicates the fill level of the filler material in the gap.
Patent Literature 2 describes an air removing tool used to discharge air remaining in a gap between a primary liner inside an existing conduit and a secondary liner inside the primary liner during the process of filling the gap with a filler material. The air removing tool includes: an air removing pipe having a leading end portion of a bamboo-spear shape; a socket having upper and lower open ends, an upper portion of the socket being fitted to a rear end of the air removing pipe; a ball valve for removing air; and a fitting, an upper portion thereof fitted to the lower portion of the socket and a lower portion thereof attached to the ball valve by screwing. The fitting of the air removing tool is screwed into an air removing hole bored through the secondary liner, and thereby the air removing tool is firmly attached to the secondary liner. The leading end of the air removing pipe is able to be brought into contact with an inner circumferential surface of the primary liner, and air in the gap is discharged through an opening of the pipe.